Circuit breaker tester



June 14, 1938. w. F. sKEATs 2,120,873

CIRCUIT BREAKER TESTER Filed Fb. 27, 1937` 5 she'ts-sheet 1 Inventor? Wilfred E Sheats,

Hi s Attoreg.

- June 14, 1938. w. F. sKEATs 2,120,873

CIRCUIT BREAKER TESTER Filed Feb. 27, 1937' 3 Sheets-Sheet 2 Inventor: I I

HIS Attorey.

June 14, 1938. r w. F. sKEA'Ars 2,120,873

` CIRCUIT BREAKER TESTER y Filed Feb. 27, 1957 5 Sheets-Sheet 3 f l Inventorz. v Wilfred E SKeata His Aitor-neg.

.Patented June 14, 1938 f alzasra PATENT ori-ICE cmcul'r naam TESTER. l Wilfred F. Skeats, Lansdowne, Pa., assignmtoy General Electric New York (lompany, a corporation of `Application February 27, 1937, Serial No. 128,217 17 claims. (cl. irs-iss) My invention relates to testing devices and con-l cerns particularly methods and devices fortesting circuit-interrupting devices at high apparent power on a low-power source.

It is'an object of my invention to provide improved, simply operating apparatus for testing circuit breakers under conditions simulating the conditionsv of short circuit at rated apparent power as they occur in actual operation.

AIt isan object of my invention to provide an arrangement which is' suitable for testing a single breaker, whether or not the breaker is of the type having positive operating characteristics, and without the necessity of synchronizing other and independent circuit operations with the interto provide a testing arrangement that Will continue to simulate actual operating conditions although the current may be reestablished in successive half cycles.

Other and further objects and advantages will become apparent as the description proceeds.v

y In accordance with my invention in its preferred form, I provide a low-voltage source for supplying normal load current to a circuit breaker to be tested. The source need have comparatively little power owing to its low voltage. One or more surge generators are provided andwthey are arranged to be released in succession, one of them being released after .each current interruption of the breaker in cases where the current is reestablished and more than one current interruption occurs. Thevoltages of the surge generators are applied to the breaker contacts to simulate the recovery voltages produced when the breaker is operating under actual voltage and power conditions. Fortripping the surge generators, electric valve apparatus'may be employed having control circuits inductively connected to the circuit supplying current to the breaker.

The invention may be understood more readily from the following detailed description when considered in connectlonwith the accompanying drawings and those features of the invention which are believed to be novel and patentable will be pointed, out in the claims appended hereto. In the drawings, Fig. '1 is a circuit diagram of one embodiment of mylnvention having a plurality of surge generators with electric valve apparatus for controlling the tripping of the surge generators, and an arrangement for causing the tripc'ontrolling apparatus to be connected to diiferent surge generators in succession after each current interruption -of the breaker; Fig. 2 is a fragl which a plurality of electric valve devices is employed `for controlling the tripping of the surge generators and the arrangement is such that the trip-controlling devices are successively connected to be responsive to circuit interruption by the circuit breaker instead of connecting the same trip-controlling apparatus to the surge generators in succession as in the'apparatus of Fig. l; Fig. 3 is a fragmentary circuit diagram representing in part a further modication of the arrangement of Fig. 1 or Fig. 2 in which the trip-controlling circuits responsive to the polarity of the current interrupted are symmetrical; Fig. 4 is a fragmentary circuit diagram of an alternative arrangement for reconnecting surge generator control circuits after thegenerators have operated; Fig. 5 is a fragmentary diagram of a modiiication in the arrangement of Fig. 1; and Fig.. 6 is a simplied arrangement for use when exceptionally high voltage surges are not needed. v'Like reference characters are utilized throughout the drawings to designate like parts.

the circuit breaker Il is supplied by a source l2 and the recovery voltages are supplied by one or more surge generators i3, i4, l5, i8, etc., depending upon how many times the circuit breaker Il is expected to reestablish the current after having broken it. The surge generators I3 t'o I6 are of the type which may be charged comparatively slowly from a source at a moderately high voltage and released to supply energy relatively quickly at considerably higher voltage, although the power for charging them may be relatively small. Electric valve apparatus Il is employed for releasing the' surge generators I3 to I6, and relays, which will be described more vin detail hereinafter are provided for connecting the release or trip-:controlling apparatus I1 to the' surge generators in succession. In order to make the `c`oil I3 is provided in'inductive relation to the circuit of the source I2 and the breaker II, and

the coil I8 is connected to control circuits ofthe oil-immersed circuit breakers, and is schematically represented as having a pair of relatively movable contacts I9. In the arrangement shown, there is an operating rod 2l for opening and closlng the contacts I 6, and there is an operating mechanism 22 of any desired type for moving the rod 2I.

Abeing dissipated -The supply circuit 'I2 is one of sufllcient current-carrying capacityv to furnish any desiredl current to the breaker II but is of low voltage.

since it need furnish only the voltage drop across the contacts I9. Preferably, a reactor 23 is interposed in the circuit I2 in order .to prevent surges produced by the surge generators I3 to I6 from damaging the supply source I2 or from therein instead oiin the circuit breaker II. However, in case the supply source I2 has sumcient inherent reactance, it will obviously 'not be necessary to utilize an independent concentrated inductance, such as shown at 23.

For the purpose of obtaining an indication or a record of the behavior of the circuit breaker II under test, oscillographs are preferably provided Whichare connected in a suitable manner.

For example, for measuring the current through the breaker I I, an osclllograph 24'may be employed. winch is connected across a shunt 25 connected in series with the supply source I2 and the circuit breaker II and, for measuring the voltage across the contacts I9, an oscillographv 26 may be provided which may, if desired, be connected through a step-down capacitative potentiometer consisting of a plurality of condensers 21 connected in series across the contacts I9, the oscillograph 26 being connected across one of the condensers 28. ,The oscillographs 24 and 26 should be so arranged that their records can be synchronized. This may be done by having the two of then record on the same rotating film, or by superimposing on each record va brief, sharp transient which will; by the time of its occurrence, indicate corresponding instants on the two time scales.y The oscillographs 24 and 26 may be of any desired type known in the art, such as cathode ray oscillographs, for example,l which are particularly useful in case of high-speed transients, but the particular type ofl the oscillograph does not constitute apart of my invention and the oscillographsand their connections need not, therefore, be described in detail. Preferably, for thesake of safety andfor Vassuring deiiniteness of the'potentials of various parts of the apparatus, one side of the supply source I2 is' grounded by means of a connection, such as the ground connection 29.

The surge generators I3 vto 'I6 are similarin construction and may be of a type .well'known in the art. It will, therefore, be suicient to refer briefly to oneoi' the surge generators, for example, the surge generator I3. 'I'here is'a plurality of condensers 30, 3|, 32, 33, andj34 connected in shunt to a source of charging current having a Y moderately high voltage ,of agiven polarity but not necessarily having a very-high current c apac' Y ity. The source of charging current may consist of a high-voltage alternating-current 4source 35' with av rectier 36 of the twoelectrode discharge-- tube type for example. One side 31 of the condenser 34 is grounded and likewise one side `of.

.denser` 34 positively. Relatively high'resistance connections 38 are provided between the condensers 3II` to 34to join the condensers in parallel with respect to the charging source 35.v A plurality or discharge .gaps46 is provided, which gaps are so connected that, with respect to the circuits through the gaps 40, the condensers 36 to -34 are in series instead .of in parallel. There is a gap 4I, in the output circuity of the surge generator I3. having a pair of electrodes 42 and 43. 'Ihe electrode 42 serves as the output terminal of the vsurge generator and the electrode 43 is connected to the high potential terminal 44 of the circuit breaker II.

Thesurge generator I3 is adjustable for producing transients of any desiredwave shape. For' this purpose, the constants, such as capacity, may be variable, and adjustable shunt -or series re- Asistances, inductances, and capacitances (not shown) may be included but, since this feature is well' known'in the art and is not a part of my invention, it need not be described in detail. In order to guard against interaction between the surge generators I3 to I6 whereby the discharge of one generator might trip the other generators, inductance coils are placed in the output leads of the surge generators, and -a high-resistance ground is placed in the circuit between .the inductance andthe surge generator, the inductance 45 being connected in series between the circuit breaker II and the electrode 43 of the gap 4I and a high-resistance 46 being connected from electrode 43 to ground.

'Ihe surge generator I4 and its connections are similar to the surge generator I3 and its connections with the exception that the discharge tube rectifier 41 of the surge generator I4 has its electrodes reversed, causing the condensers of thesurge generator I4 to be charged with the opposite polarity and causing a surge of the opposite polarity to be provided by the surge generator 'I4 when released. In a similar manner,

the polarities of the surge generators. I5 and I6 and any additional generators which may be provided are alternately reversed.`

For the purposeA of tripping or releasing the surge generators, means are provided for applying -a voltage suddenly to one of the gaps 46, causing it to break down', whereupon the transient produced will break down all of the gaps and trip `-the entire surge generator.

paratus for tripping the surge generators is so arranged that, upon the interruption of current by Y the breaker II, a suitable trippingvoltage is applied to the surge generator and a recovery voltagetransient is applied to the contacts I6 di- Vrectly following current interruption in the same manner as in actual full-power operation of cir-v cuit breakers. The tripping voltage for the surge .generators is provided by the electric valve aptransformer having a primary winding connected in series with the circuit breaker II, or the coil 'I8 may merely be so placed as to have some mutual inductance'with respect to the 'circuit of 'I'he control ap-' 2,120,873 the breaker II. The condenser 48 and the re'-` "sult from a current zero during the arcing period,

a condenser 39 may be connected across the resistor 49 anda second resistance 49a. may be connected in series with the combination, or an additional inductance 49b maybe placed in the y of the circuit breaker l I. The arrangement is such that the switch 5I is closed at an early point in the opening stroke of the circuit breaker I I. For example, the flexibility of the movable con- `tact I9 or its supports may be such that the switch 5I -closes before Ythe circuit breaker II actually opens. The switch 5I is interposed in a connection between the resistor49 and the control zero. The voltage across the condenser 48, being circuits of the trip-controlling apparatus I1.

The trip-controlling apparatus I1 comprises a lpair of three-element electric valves 53 and 54,

which may be discharge devices or. discharge tubes, having suitable sources of anode current 55 and 56 and sources of grid-biasing potential 51 and 58. respectively. The discharge tube 53 consists of'a gas or vapor filled envelope 59 con-4 taining an anode 68, a cathode 6I having a source of heating current not shown, and a grid or control electrode 62. Similarly,vthe discharge tube 54 includes an anode 63, a cathode Sand a grid or control electrode 65. A resistor 52 having high resistance is connected from the input side of the grid-biasing potential source 51 to the cathode 6I of the tube 53 in order to prevent accumulation of stray charges on the grid 62 which might cause false tripping of thetube.

A resistor 66 is connected between the positive terminal of the anode source 55 and the anode 60 of the tube 53. The negative side of the source 55 is connected to the cathode 5I of the tube 53 through the resistor 49 and the switch 5I. The resistor 52 is in parallel with the resistor 49 but carries a relatively small proportion of the 'current owing to its higher resistance. The anode current source 58 has its positive terminal connected to the anode 53 of the tube 54 and its negative side is connected to the cathode 64 of the tube 54 through a resistor 61. The

. anode 60 of the tube A53 is connected through a lays 12 and 13, respectively, the'purpose of which will be described hereinafter in connection with tests in which the circuit breaker is expected to Ireestablish the current more than once.

The operation of the Aapparatus thus far de-y scribed is as follows: l

Let it be assumedthat the current ysource I2 is causing current of a predetermined value to current remains zero or substantially so.

senting the short-circuit current for which the test is to be made.l The interrupting characteristics of the circuit breaker II are then tested by causing the operating mechanism 22 to separate the contacts I9 whereupon the switch 5I is closed and the surge generator tripping apparatus I1 is connected in readiness to cause a recovery voltage transient to be applied between the contacts i 9 when the arc is broken between these contacts.

It is obvious that, during the normal flow-of current through the breaker II, a voltage will be induced in the coil I8 by the sine wave variations in current in the circuit of the source I2, as suming this is an alternating-current circuit, and, ol course, no voltage will be induced in case the test is made with a steady direct current and the source I2 is a direct-current source. The greater part of whatever voltage is induced will appear across the condenser 48. When the breaker attempts to clear, however, the rate of change of current will change suddenly from a high rate, as the current approaches zero, to zero as the The 3 `flow through thecircuit breaker I I', the contacts vof which are closed, the current iilowing reprevoltage of the mutual inductance or coil I8 will likewise change suddenly from ahigh value to voltage impulse will be furnished to one or the other of the control grids $2 or 65 of the discharge tube apparatus l1.

Assume that the polarity is such as to raise the voltage of the grid 82 of the tube 53 controlling the surge generator I3. The rise in po-y A tential of the grid 62 will re the discharge tube 53, causing current to fioW through theresistor 65, thereby suddenly depressing the potential of the anode 60 and causing a sudden drop in p o tential to be transmitted to the gap electrode 5 9 through the condenser 68. The side 38 of thev gap 4@ is normally charged to positive potential and, accordingly, a sudden drop in the potential of the electrode 59 will increase the potential difference between the electrodes and initiate a discharge across the gap which, in turn, will cause all the gaps 48 of the generator I3ito` discharge and an impulse at high voltage will cross the gap 42, impressing a recovery volt-age transieht-on the circuit breaker II. Although the condensers to 34 are in parallel with respect to current supplied through the rectifier 36 and the resistances 39, they are in series withrespect to a circuit through thegaps 40. When thegaps 48 are broken down, the'conductivities of the resistances 39 are negligible in comparison and a very high voltage transient is delivered by the surge generator. It will be' understood that the connections are such that the polarity of the surgeprovided by the generator I3`corresponds to the polarity of the recovery voltage transient which Would occur in the circuit breaker II, interrupting current in a circuit operating at full power and voltage.

If thedirection of the current in the circuit breaker II had been opposite, the potential of the grid 62 would.v have been depressed insteadA pressed, causing the discharg'eftu be 54 yto nre.

through the resistor 81 would suddenly have raised the potentialV of the cathode 34,y causing a raising of the potential of the electrode 1I of the gap 40' of the surge generator I4. It will be recalled that the condensers of the surge generator I4 were so charged that the side 33' of the condenser 34 was negative with respect to electrode 1I and, consequently, raising the potential of the electrode. will initiate a discharge in the surge generator I4 resulting in the application of a recovery voltage transient to the circuit breaker II of the opposite polarity to that furnished by the surge generator I3.

Whichever of the two .surge generators I3 or I4 discharges rst, it will be understood that, upon the interruptionof the next half cycle of current, 'the current direction will be the oppo-v site and accordingly the other of the two surge' generators will be released, thus simulating actual conditions under. which, if the currentis reestablished after the ilrst interruption, a recovery voltage of Areversed polarity will -occur after the second interruption. j

In response to the rst surge, the tested breaker may either maintain an open circuit or y break down along the previous arc path. In the former vcase, if the surge is made to simulate a given recovery transient in shape, the circuit has established the ability of a breaker to clear the applied current in combination with that recovery transient, which may correspond to a much higher 60 cycle voltage than that at which the current was supplied. In the latter case, the circuit is reestablshed through the tes't breaker and current from the 60 cycle source will flow for another half cycle after which the second surge generator will be discharged, giving the test breaker a second opportunity to clear against a highvoltage surge.

Should the circuit breaker II -fail to clear on the discharge of the second surge generator, it

will, as far as the circuit thus far explained,

including only surge generators I3 and I4, is concerned, have lost its last opportunity to clear against the -high voltage surge. Even in this case, however, the circuit may have performed a rating of the breaker exceeds the current which the testing plant is able to deliver at rated voltage, it is customary to check the mechanical `forces by tests at rated current or more but at reduced voltage. These forces are, to somel extent, dependent upon arc duration, however, and the arc duration may decrease with reduction in test voltage so that, in many cases, such testing isl either not fully effective or requires compensation for short arc lengths by increase of current beyond rating, which attempts to compensate for understress at' one instant during the interruption period by overstress at another. In such a case, it is always open to questionwhether the compensation is insufficient or excessive or y 8,190,878 I4 'of the discharge tube 54 would have 4been delarity. Similarly,

in another at 'the same time. The` use of the circuit described with surge generators I3 and I4, however,. increases the arc duration by oneV or two half cycles and this is. usually suiiicient to render it equal to that obtained at full voltage. Thus themechanical forces, which depend directly only on current and arc duration, will be the same in these tests at reduced voltage as in full voltage tests.

Should it be required to prolong the arcing still further or actually to clear the circuit against a high voltage surge where this is not accomplished with the application of two surges, further surges may be obtained by the use of any adl dltional number of sur-ge generators, such as the generators I5 and I6, in combination with relaying devices, such as the devices 12 and 13. For example, the relaying device 12 may be actuated by the discharge current fromv the surge 'generator I3 -to disconnect the anode 80 f the discharge tube 53 from the surge generator' I3 and to connect the anode Blitothe third surge generator I5, which will operate on the third or the fourth attempt to clear, depending upon po-v` vthe relaying device 13 will effect a transfer of the connection of the cathode 64 of the discharge tube. 54 from the surge generator I4 to the surge generator I 3 supplying a surge of polarity opposite to that of generator I5.

'I'he relaying device 12 having a yoke 14 of magnetizable material, such as soft iron, an armature 15, a movable contact 16 mechanically connected to the armature ,15,

two pairs of stationary contacts11 and 13 co' operating with the movable contact 15, and a snap-action spring 19 for holding the movable contact 13 in engagement with one or' the other of the pairs of stationary contacts 11 and 13. The yoke 14 links one of the current-carrying conductors of the' surge generator I3; for example, it may link one of the leads of the lowermostl condenser 33 connected between the points 31 and 38. 'I'he lower stationary contacts 11 are in the connection between the condenser 33 and the surge generator I3 and, before tests are made, the apparatus is placed in its initial position with the movable contacts 15- downward engaging the contacts 11 so that theflrst'impulse delivered through the discharge tube 53 causes thesurge generator I3 to deliver a surge to the circuit breaker II. Thereupon, the yoke 14 picks up the armature movable contact 16 to engage the upper sta tionary contacts 1li.4 The anode 60 of the dis! charge tube 53 is now connected through the condenser 63 to the surge generator I5. :The connection to the surge generator I5 corresponds to that formerly existing to the surge generator I3 and accordingly, upon the next operation of the discharge tube 53, the surge generator I5 will deliver a surge.

'Ihe construction and connections of the relayingA device 13 are similar with the exception that the relaying device 13 transfers the connection of the cathode 64 of the discharge tube 54 and the condenser 10 from the surge generator I4 to the surge generator I6. If additionalv surge generators are desired, additional relays corresponding tol 12' and 13 may, of course, be employed so asto transfer the connection from the' surge generator which has just been'` released to much more slowly than discharged, are capable possibly insuiiicient in one respect and excessive is of the pick-up type 15 and causes the of becoming charged and being ready to deliver another surge within several half' cycles and, if desired, the last pair of surge generators may have relays arranged directly or indirectly to transfer connections back to the iirst pair of f surge generators I3 and I4. For example, the

as the relays 12 and 13, respectively, of all the previous surge generators of each polarity to the lower p'osition.

With only four surge generators, however, a

direct mechanical connection may be employed, as illustrated in Fig. 4, and the relay 8| of Fig. 1 may be replaced by a yoke 85 andan armature connected to the contact-operating rod 80 of the relay 12. The yoke 85 will be reversed pair of stationary contacts 96 of the relay de' in position with respect to the yoke 14 so that, when the surge generator I5 is released,V the yoke 85 will draw down the armature 86 and restore the 'movable contact 16 to its lower position `in engagement with the stationary contacts 11. vThe construction and arrangement of parts replacing the relay 82 are similar to those shown inl Fig. 4 and serve to restore the movable contact of the relay '13 to its lower position upon g release of the surge generatorllij In the arrangement of Fig.v 2, separate pairs of discharge tubes` 53 and 54, 81 and 88, etc., are employed for controlling successive pairs of surge generators I3 and I4, I5 and I6, etc.

The purpose of this arrangement is to 'permit lead 94 connecting theterminal 95 of the auxiliary switch 5| to the grid-biasing potential source 51 of the discharge tube 53. The upper vice 89 is interposed in a-lead 91 from the terminal `95 of the auxiliary switch 5| to the gridbiasing potential source 98 of a discharge tube 81 having an anode 99 connected through a condenser to a Asuitable control point in the surge generator I5. Thus, after the surge generator I3 has operated, the movable contact will close the stationary contactsSB and cause the surge generator. I to be released by the firing .of the tube 81 upon the next circuit-breaker y'current interruption of the polarity which previously released-the surge generator I3. Likewise, the relay device 90 rhas a lower ,pair of stationary contacts |,0I` interposed in the grid circuit of the discharge tube54, and an'upper pair of stationary 1contacts vI02'interposed in the grid circuitv of the dischargevtube 88, the latter discharge tube having Va cathode |03 connected through a condenserv |04 vto a suitable lpoint in the surge generator lII. It will be observed that the grid leak resistor 52 of Fig. 1

is replaced by separate grid leaks 52a, 52b,.52c,

and 52d, one for each tube, in 2.

There are relay -de- Fig. 3 illustrates a modification in the arrangeare controlled by raising the grid potentials with respect to ground instead of controlling one discharge tube, such as the -discharge tube 53, by raising the potential of its grid 62 above ground potential and controlling' the other discharge tube 54 by lowering the potential of its cathode v|54 below ground potential. In the arrangement of Fig. 3, the resistor 49 of Figs. l and 2 is replaced by a corresponding resistor |05 having a midterminal |06 andend terminals |01 and |08, the end terminals |01 and |08 being connected across the condenser` 50 of Figs. 1 and 2. The switch 5| of Fig. 1 is replaced by a double-pole switch |09 .having separate blades |I0 and III interposed in the circuits from the end terminals |01 and |08, respectively, of the resistor |05. The midterminal |06 of the resistor |05 is grounded. 'I'he resistor 52 of Figs. l and 2 is also replaced by a resistor ||2 having a midterminal II3 connected to the midterminal |06 of resistor |05 and having-end terminals II4 and` I I5 adapted to be connected to end terminals |01 and |08, respectively, of the resistor |05 when the switch l|09 and the relaying devices 89 and 90 are closed.

'I'he end terminal I I4 of the resistor I I2 is connected to the grid 62 of the discharge tube 53 analogous to the arrangement of Figs. l and 2. 'Ihe cathode connection of .the discharge tube 53, however, is made to the midpoints |06 and II3 of the resistors |05 and I|2 instead of tothe remaining end point of the resistor 52, as in Figs. 1 and 2, and the grid connection of the discharge `tube 54'is made to the end point I|5 of the resister I I2. The contacts 93 and I0'I of the transfer relays 89 and 90, respectively, may be interposed, if desired, in series with the contacts IIO and III.

It will be understood that, for the purpose of applying successive surges when current is reestablished through the breaker more than twice,

the transfer relay arrangement of either Fig. l or Fig. 2 may be utilized in connection with the tube connection of Fig. 3. If the transfer arrangement of Fig. 2 is used, there will be a plurality of pairs of'tubes, such as 53 and 54, with transfer relays including contacts 93 and |0I for v'transferring connections. IIn this case, the contacts 11 will not be employed. On` the other hand, if the transfer arrangement of Fig. l is used, the contacts 93 and I0| will be omitted, only one pair of tubes 53 and 54 will befneeded, and the transfer of connections will take place through relays connected as shown at 12, 13, 8|,

Y potential whereas, when an impulse of the other polarity is induced in the coil I8, the otherdischarge tube grid 65 Will be raised in potential. In this manner, the discharge tube 54 as Well as the dischargetube 53 is fired by having its grid potential raised, the cathodes of both tubes being normally grounded.

Under certain circumstances where particularly greatvspeed .of response is desired, it may be preferable to modify the arrangements of Figs. 1,2, and 3 by changingthe connections of the Vgridcontrolled discharge tubes and using'threeelectrode gaps in alternate surge generators`V for initiating the discharge. [The modification of the circuits of the embodiment'of Fig. 1 for this purpose is illustrated in Fig. 5. Corresponding changes in tube connection may likewise be made in the embodiments of Figs. 2 and 3.

In the arrangement represented by Fig. 5, negyative voltage impulses are utilized to trip each of the surge generators. The vnegative side oi' x the voltage source 55 is connected directly to the The resistor 51 in thecathode 6| of the tube 53. cathode'lead of the tube 54 is replaced by a resistor 51 in the anode lead of the tube. The electrode 89v oi' the lowermost gap 40 of the surge generator I3 is connected through the condenser 53 to the anode 6|| of the tube- 53 as in the arrangements previously. described. 'However, thelowermost gap 40'- of the surge generator |4 or tube 53 through the condenser 68, and the middle of any other surge generators I5, etc., having the same polarity, in the arrangements previously described, is replaced by a three-electrode gap |2| having an electrode v|22 substantially at ground potential prior to discharge, a negative electrode |23,- and a middle electrode |24. A high-resistance resistor |25 is connected between Vthe electrodes |22 and |23, and the electrode |24 is connectedto an intermediate point'in the re'- v sistor |25 for the purpose oi' holding'the'midf dle electrode |24 normally at a potential intermediate the potentials of theelectrodes |22.and

|23. 'I'he anode 53 of the tube 54 is connected to the middle electrode |24 of the gap |2| through the condenser 10 and .also through the conof the voltage drop in the resistance 51' and thel potential of the middle electrode |2 4 of the gap |2| is depressed. In consequence, the diil'erence in potential between the electrodes |22 and |24.

causes this portion of the gap to break down.` .A discharge of all the condensers of the surge generator |4 is thereby initiated and a voltage-surge is applied to the circuit breaker Il. y

In Figs. 1 to 5, I have illustrated arrangements in which my invention.` is employed in conv` nection with surge generators suitable fordeliveringextremely high voltage surges. However,

in cases where such high voltages are not needed, simpler types of surge generators may be em'- ployed. For example, in the arrangement illustrated in Fig. 6, two-condensers |25 and |21 serve as generators for surges of opposite polarities...

Two three-electrode gaps |28 and |29 are employedv for controling the surges and'V delivering them 'to the high-voltage terminal 44 of the circuit breaker the gap |28 is connected to the anode 80 of the terminal |3| of the gap |29 is connected to the anode 83 of the tube 54.

As in the arrangements previously described,

' one or the other of the tubes 53 and 54 becomes conducting upon the interruption of current by the breaker depending upon the polarityo! the current interrupted. When either tube 53 or 54 becomes conducting, the potential of the corresponding middle electrode |30 or 3| ofthe three-electrode gaps is depressed and a discharge takes place from the middle'electrode to one of The middle electrode |30 -of the adjacent electrodes, thereby initiating vs. discharge of the corresponding condenser |24 or l|21 and applying a voltage surge to the circuit breaker Il.

I have herein shown and particularly described certain embodiments of my invention and certain methods oi' operation embraced therein for the purpose of explaining its principle and show ing its application but it will be obvious to thpse skilled in the art that many modiilcations and variations are possible and I aim, therefore, to cover all such modiilcations and variations as fall within the scope of my invention lwhich is deiined in the appended claims.

What I claim as new, and'desire to secure by LettersPatent ofthe UnitedStates, is:-

l. AApparatus iortesting circuit interrupting devices comprising in combination, a supply circuit ior current to be interrupted by an interrupting device under test, a coil .in inductive relation to said circuit, a capacitor and a resistor in s .eries with saidcoil, a surge generator con- I nected tov said circuit, and means responsive to voltagev across saidv resistor i'or releasing said surge generator. 'i

2. Apparatus f or testing circuit interrupting devicesV comprising incombination with a circuit interrupting `device under test, an operating member, means 'i'orj passing testcurrent in a circuit through said device', a surge generator withV terminals connected across said device and vwith, a control terminal, a coil in inductive re lation to said circuit through said device, a condenser andA a resistor in series ,with said coil, a

-second resistor, aswitch so connected mechanically to saidoperating member asto close when said interrupting device is open and so connected electrically to said resistors as to connect theml in' shunt when said switch is`closed, a discharge device with a grid circuit including said second resistor, a current source,va third resistor, said source being connected in series to constitute a discharge devi'ce, thirdyresistor, and current discharge circuit, and a capacitative connection to said surge generator control terminal from a point in said discharge circuit between said third resistor and said discharge device.

3. .Apparatus `for testing circuit interrupting 'devices comprising incombin'ation with a circuit interrupting device undertst, means for passing testing 'current in -a vcircuit through said device,

a surge generator with terminals connected across said device and with-a control terminal, impulse-producing means responsive to sudden cessation of current inthe circuit through said device, adischarge-tube device having a control electrode connected to said impulse-producing means and including a resistor in a discharge circuit controlled by said electrode, and means 'for transmitting potential variation from said resistor to the control terminal. of said surge generator upon excitation of said control electrode to produce a discharge .through said resistor.

4. Apparatus for testing circuit interrupting devices comprising in combination, a circuit for passing testing current` through a device to be tested, impulse-producing means responsive to sudden cessation oi current through said circuit, a surge generator having output terminals for connection across a circuit breaker to be tested and a 'control terminal, and `voltage variation producing means connected to said control ter- I minal'having a control electrode connected to said impulse-producingv means.

testing circuit for releasing said surge generator.

6. Apparatus for ytesting circuit interrupting devices comprising in combinationjwith a circuit interrupting device under test, means for passi ing testing current in a circuit #through said device, a pair of surge generators of opposite polarity, 'each with terminals connected across said device and each with a control terminal, voltage impulse producing means responsive to sudden cessation of current in the circuit through V said device, a pair of discharge devices having control electrodes yconnected to said voltage impulse producing means and vresponsive to impulses of opposite polarities and having resistance-including discharge circuits controlled by said electrodes, a connection between the control terminal I of one of said surge generators and va point in the discharge circuit of one of said discharge devices, and a connection between the control terminal of the other of said surge generators and a point in the discharge circuit of the other Y of said discharge devices.

'7. Apparatus for testing circuit interrupting devices comprising a circuit for passing a shortcircuit simulating current through a circuit in terrupting device to be tested, a pair Aof surge Agenerators of opposite .polarities for applying recovery voltage ltransients to a circuit interrupting device to be tested, voltage variation producing means having control electrodes responsive to voltage impulses of opposite pola.ritie`s,

connections between said voltage 4variation producing means and said surge generators for releasing one or the other of said generators according to which control electrode is excited,v

and voltage impulse producing means responsive to sudden cessation -of current in said testing circuit and connected to said control electrodes.

8. Apparatus for testing circuit interrupting devices comprising a circuit for passing a current through a circuit interrupting device to be tested, a plurality ofsurge generators of alternately opposite polarities for applying recovery voltage transients to a circuit interrupting device to be tested, a voltage impulse producing means responsive to sudden cessation of current in the testing currentcircult, discharge apparatus for producing voltage variations to release said surge generators having output terminals adapted to be connected to said surge generators and control electrodes responsive to vvoltages of opposite polarity connected to said voltage impulse producingmeans, and means for transferring the 'connections of said discharge apparatus from a preceding surge generator to a subsequent surge lgenerator in response to operation of the prefor releasing it, each discharge device having a control electrode, voltage-impulse producing means responsive to sudden cessation of current in said testing circuit, and relay devices for'connecting said impulse-producing means to successive control electrodes in response to successive operation of said surge generators.

10. A device for testing circuit interrupting devices comprising a circuit for passing a testing t current' through a circuit interrupting device to be tested, a plurality of surge generators for ap` erators, each relay deviceV being responsive to release of an associated surge generator to transfer the connection oi the voltage impulse producing means irom a preceding surge generator to a subsequent surge generator, and a relay device associated with the last surge generator responsive to release thereof to restore said flrst mentioned relay devices to their initial position.

11. A device for testing circuit interrupting devices comprising in combination, a circuit for passing' a testing current through a, circuit interrupting device to be tested, a-pair of surge generators for applying recovery voltage transients to the device being tested, impulse-.producing means responsive -to sudden cessation of current'in the testing circuit, connecting means between ksaid impulse-producing means and said surge generators ior causing release of said surge generators upon production of an impulse, a

rel-ay device having a pair of operating mecha-l nisms, one of which is responsive to release of one surge generator .and the other of which is responsive .to release of the other surge generator, and a transfer element actuated by said operating elements for transferring the connection of said impulse-producing means from one surge 'generator tothe other and vice versa.

12. Apparatus for testing circuit interrupting devices comprising in combination, a supply circuit for current to be interrupted by a circuit interrupting device under test, a coil in inductive relation to said circuit, a capacitor and a resistor in series with said coil, a surge generator connected to said circuit; and means responsive to voltage across said resistor for transferring a voltage impulse to said surge generator.

13. Apparatus for testing circuit interrupting devices comprising in combination, a supply circuit for current to be interrupted by a device under test, a surge generator for applying a recovery voltage transient to the circuit interruptf ing device under test, 'impulse-producing means responsive to a sudden cessation of current from the supply circuit, and means for transferring impulses from said impulse-producing means to said surge generator for releasing it.

14. A device for testing circuit interrupting devices comprising in combinationfa circuit for passing a. test current through a circuit interrupting device to be tested, a plurality of surge generators for applying recoveryl voltage transients to the device being tested, impulse-producing means responsive to sudden cessation of current in the testing circuit, connecting means between said impulse-producing meansy and said surge generators for causing release of said surge generators upon 'production of 'an impulse, and

lrelay devices, each responsive to release of an associated surge generator to transfer lthe connection of the voltage impulse-producing means from a preceding surge generator to a subsequent surge generator.- i

-15.Apparatus for testing circuit interrupting devices comprising, a circuit for passing a load simulating current through 'a circuit interrupting device to be tested, a pair of surge generators of opposite polarities for applying recovery voltage transients to a circuit interrupting device to be tested, a voltage impulse-producing means responsive to sudden cessation of current in said testing circuit,'and means for selectively transterring impulses of opposite polarity from said voltage impulse-producing means to one or the other of said surge generators for releasing it.

16. Apparatus lfor testing circuit-interrupting devices comprising in combination, a circuit for passing a testing current through a circuit-interrupting device, a pair of surge generators of-oppo .site polarity for applying recovery voltage transients to a circuit-interrupting device, and means responsive to sudden cessation of current in said testing circuits for releasing one or the other of said surge generators laccording to the polarity of the current flow interrupted in the testing circuit.

17. Apparatus vfor testing circmt-interrupting devices 'comprising in combination, a circuit for passing a testing current through a circuit-interrupting device, a plurality of surge generators'oi' alternately opposite polarity for applying recovery voltage transients to a circuit-interrupting device, and means responsive to sudden cessation of current in said testing circuit for selectively releasing said surge generators.

WILFREID F.' BKEATS. 

